Cigarette filters



United States Patent Ofi ice Patented Jan. 28, 1969 US. or. 131-267 3 Claims Int. c1. A24f 13/06 ABSTRACT OF THE DISCLOSURE A cigarette filter made of cellulose ester filaments, which in order to increase their absorbing capacity, are impregnated with an acidic carboxylic acid alkyl ester.

This invention relates to cigarette filters.

Cigarette filters are conventionally made of cellulose acetate or another fibrous cellulose ester and it has been proposed that the absorbency of such filters should be increased by impregnating the fibrous mate-rial with suitable absorbing agents. Many absorbing agents have the disadvantage, however, that they alter the flavour of the smoke.

It has also been proposed to modify the cellulose material itself for the same purpose. Thus, it has been proposed that cellulose esters having residues containing free acid groups, in place of the hydroxyl groups of the cellulose, should be used. For example, acid phthalate cellulose acetate, acid succinate cellulose, acid citrate cellulose or acid phosphate cellulose have a good absorbency for alkaline substances in smoke but, at the same time, the fibres are more brittle than those of cellulose acetate and are therefore less suitable for use as cigarette filters. Also, the fibres tend to age more quickly with the result that during the use of such filters, pieces of fibre break off and ibecome entrained with the smoke.

It is therefore an object of the present invention to provide a cigarette filter of improved efiiciency.

I have now discovered that a cigarette filter of improved efiiciency is obtained by treating the fibrous cellulosic material with an acidic carboxylic acid alkyl ester.

Thus, the cigarette filters according to the present invention comprise a fibrous cellulosic mass impregnated with an acidic carboxylic acid alkyl ester. Generally, the fibrous cellulosic mass will be composed of a cellulose ester, more generally cellulose acetate.

In addition to the acid ester the filter may also contain glyceryl triacetate (triacetin), preferably in a proportion of 3 parts by weight of the acid ester to parts by weight of glycerin triacetate.

All organic polycarboxylic acids which are physiologioally acceptable may be used for the preparation of the acid esters, for example, citric acid, tartaric acid, succinic acid, malic acid or saccharic acid. The acid is partially esterified with a physiologically acceptable alcohol such as, in particular, ethanol, to leave at least one free carboxyl group. Acids which contain free hydroxyl groups or hydroxyl groups esterified with monobasic organic acids, such as acetic or propionic acid, or polycarboxylic acids may be used.

The acid ester is preferably used in finely-divided form, mixed with glycerin triacetate if desired, and is applied to the outer surfaces of the fibres to form a film-like coating on the fibres. The coating may be applied by spraying or by passing the fibres through a bath of the coating material.

The filters containing the acid esters have an improved absorption efiiciency, particularly with respect to the removal of alkaline components such as nicotine, from the smoke and this is effected without the free hydroxyl groupcontaining additive introduced by the treatment being entrained in the smoke and inhaled by the smoker. This is believed to be due to the fact that the additive is simultaneously a cross-linking and hardening agent for the cellulose acetate and that it enters into a close bond with the external surface of the cellulose fibres.

In the following table, examples are given (by way of illustration only) to show the effect of the acid esters used in accordance with the invention. The absorbency of filters treated with various acid esters was compared with conventional filters. The tensile strength of the filters is also given.

TABLE Filter Specific Degree of Additive length Titer tensile nicotine (mm) (den) strength absorption (mm. WS) (percent) (1) Citric acid diethyl ester 14 5/78. 000 30 38 (2) Triacetin alone (comparison) 14 5/78. 000 29 29 (3) Diacetyl tartaric acid monoethyl ester 14 3/58. 000 33. 3 41. 2 (4) Malonic acid monoethyl ester 14 3/58. 000 33. 4 40. 2 (5) Tartaric acid monoethyl ester 14 3/58. 000 35. 1 41. 5 (6) Malic acid monoethyl ester 14 3/58. 000 32. 9 39. 6 (7) Aeetyl citric acid ethyl ester 14 3/58. 000 33. 4 41. 2 (8) Triacetin alone (comparison) 14 3/58. 000 34. 1 31. 5 (9) Maionic acid monoethyl ester 14 5/78. 000 30. 7 38. 2 (10) Triaeetin alone (comparison) 14 5/78. 000 26. 4 29. 8

The additives were added to triacetin (30% of the additive by weight) and the mixture used to impregnate the filter in proportion of 9% with respect to the weight of the filter.

The degree of direct absorption for nicotine was determined in accordance with the standard procedure of the Cigarette Industry Association.

The direct absorption of nicotine is shown in the above table to be rather more than 25% higher than that of conventional filters, without the mechanical properties of the filter being deleteriously affected.

We claim:

1. A cigarette filter comprising a mass of cellulose acetate fibres impregnated with 'an acidic carboxylic acid alkyl ester.

2. The structure as set forth in claim 1 in which the ester is diethyl citrate.

3. The structure as set forth in claim 1 in which the cellulose acetate fibres are impregnated both with the acid ester and with glyceryl triacetate.

References Cited UNITED STATES PATENTS 3,025,861 3/1962 Cobb 131267 3,144,024 8/1964 Eichwaldetal 131-267 3,285,255 11/1966 Touey a a1 131-267 FOREIGN PATENTS 570,399 2/1959 Canada.

SAMUEL KO'REN, Primary Examiner.

D. J. DONOHUE, Assistant Examiner. 

